The infectious salmon anemia virus has been identified in 12 different fish farms in eastern Maine. Although fish that have reached their adult size of 8 to 10 pounds can still be sold, more than 900,000 fish have been marketed at below market size, or euthanatized since March, when the virus hit home at Cobscook Bay. More than half of Maine's 800 acres of salmon pens are in that bay.
In the past decade, Maine's salmon industry has grown, with 2001's production bringing in an estimated $65 million. Although the virus is harmless to humans, and salmon is still being sent to market, the blow to the industry continues to be costly.
|Lesions on the gills of an Atlantic salmon with infectious salmon anemia.|
Since March, the Maine Aquaculture Association has adopted an industry-wide Infectious Salmon Anemia Action Plan, designed to ensure the containment and control of the virus. This plan is the result of an initial position paper on ISA from the Eastern Association of Aquaculture Veterinarians, a Canadian organization. Dr. Paul Waterstrat, veterinarian for the Maine Department of Marine Resources, is one of several veterinarians working to manage the disease.
"The state of Maine endorsed that plan, which is constantly in the state of revision as we learn more things about ISA," Dr. Waterstrat said.
According to the U.S. Department of Agriculture's Animal and Plant Health Inspection Service, clinical signs of ISA, also called hemorrhagic kidney syndrome, generally appear two to four weeks after infection. Signs include lethargy, swelling and hemorrhaging in the kidneys and other organs, protruding eyes, pale gills, darkening of the caudal portion of the gut, and swelling of the spleen.
Transmission occurs by direct contact with parts from infected fish, contact with equipment contaminated from contact with infected fish, with people who handled infected fish, and with sea lice.
Risk factors have been identified as proximity of less than 5 kilometers to a processing plant; exposure to suboptimally treated wastewater from processing plants and water mixed with blood from harvesting operations; improper handling and disposal of dead and drying fish; and movement of farm personnel, divers, and equipment between multiple marine sites.
|Workers monitoring an open water fish pen in Maine.|
Tightened biosecurity since the original detection has been implemented at the site source, a cage stocked with about 68,000 smolts. The cage has been isolated, and dead fish are removed daily for landfill burial. The USDA-APHIS Center for Emerging Issues reported that increased surveillance of neighboring cages and areas, the most effective measure against the virus spreading, and disinfection of equipment have been initiated. "We have instituted an emergency rule, which restricts traffic and increases the level of surveillance," Dr. Waterstrat said.
The Maine Department of Marine Resources is trying to implement a similar system that has worked for bordering New Brunswick, Canada, where the disease has been present for the past three years. The area has had a federally funded indemnity plan in place that allowed New Brunswick to stabilize the situation, and mobilize resources, after the aggressive removal of thousands of fish.
For now, the disease has been confined to the state, but Maine's biggest concern is the other aquaculture sites further down the Atlantic coast. The industry has been hit hard; the price of fish is going down. Also, the companies that are demanding control and surveillance are paying out of pocket for the precaution.
"Their resources to deal with the disease are reduced and, to a certain extent, ours are, too," Dr. Waterstrat said.
He is pleased, however, with the veterinarians the aquaculture companies have consulted with to control this disease.
"There are probably more veterinarians working with fish health here than in any part of the country right now," he said.